Silicone elastomers have been bonded to various substrates with primer compositions. For example, U.S. Pat. No. 4,133,938 to Bingham describes a primer composition which is obtained from the reaction of an acrylate and an acryloxyalkyl-alkoxysilane for bonding silicone elastomers to porous substrates.
Also, U.S. Pat. No. 4,431,472 to Hohl et al describes primer compositions which have been employed to improve the adhesion of elastomers, derived from crosslinkable compositions based on diorganopolysiloxanes containing rod-shaped copolymers formed by the free-radical copolymerization of styrene and acrylic acid ester in the presence of the diorganopolysiloxanes, to undercoatings consisting of epoxy resin and pitch or tar. The primer composition described therein consists of a mixture containing a silane having an SiC-bonded aliphatic multiple bond and a silane having an SiC-bonded epoxy group. The primer composition is applied to the undercoating prior to the application of the crosslinkable organopolysiloxane composition.
Therefore, it is an object of the present invention to provide bonding between organopolysiloxane elastomers which are derived from crosslinkable compositions based on diorganopolysiloxanes containing insitu generated rod-shaped copolymers formed from the free-radical copolymerization of styrene and acrylic acid ester and coatings based on an epoxy resin and pitch or tar, which bond is particularly strong and stable when exposed to water, especially water which contains inorganic salts such as sea water.
Another object of the present invention is to provide a method for improving the adhesion of organopolysiloxane elastomers to substrates. Still another object of the present invention is to provide a method for improving the adhesion of organopolysiloxane elastomers to substrates coated with an epoxy resin and pitch or tar. A further object of the present invention is to provide a method for improving the adhesion of organopolysiloxane elastomers which are derived from compositions containing diorganopolysiloxanes which are crosslinked by a condensation reaction and contain insitu generated rod-shaped copolymers which are obtained from the free-radical copolymerization of styrene and an acrylic acid ester. A still further object of the present invention is to provide a substrate having an undercoating of an epoxy resin and pitch or tar and an overcoating of organopolysiloxane elastomers which are derived from crosslinkable compositions based on diorganopolysiloxanes containing insitu generated rod-shaped copolymers obtained from the free-radical copolymerization of styrene and an acrylic acid ester in the presence of the diorganopolysiloxanes.